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Define viscosity and coefficient of viscosity. Write SI unit and dimensional formula of coefficient of viscosity.

Important Questions on Mechanical Properties of Fluids

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A bubble of radius R in water of density ρ is expanding uniformly at speed v. Given that water is incompressible, the kinetic energy of water being pushed is
EASY
Physical processes are sometimes described visually by lines. Only the following can cross
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The platelets are drifting with the blood flowing in a streamline flow through a horizontal artery as shown below:

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Artery is contracted in region II. Choose the correct statement.

EASY
A air bubble of radius 1 cm in water has an upward acceleration of 9.8 cm s2. The density of water is 1 gm cm3 and water offers negligible drag force on the bubble. The mass of the bubble is g = 980 cm/s2.
MEDIUM

What will be the nature of flow of water from a circular tap, when its flow rate increased from 0.18 L min-1 to 0.48 L min-1? The radius of the tap and viscosity of water are 0.5 cm and 10-3 Pa s, respectively. (Density of water : 103 kg m-3)

EASY
If p is the density and η is coefficient of viscosity of fluid which flows with a speed v in the pipe of diameter d, the correct formula for Reynolds number Re is
HARD
A very large block of ice of the size of a volleyball court and of uniform thickness of 8 m is floating on water. A person standing near its edge wishes to fetch a bucketful of water using a rope. The smallest length of rope required for this is about
MEDIUM
The approximate depth of an ocean is 2700 m . The compressibility of water is 45.4×10-11 Pa-1 and density of water is 103  kg/m 3. What fractional compression of water will be obtained at the bottom of the ocean ?
MEDIUM
If it takes 5 minutes to fill a 15 litre bucket from a water tap of diameter 2π cm then the Reynolds number for the flow is (density of water = 103  kg/m3 and viscosity of water=10-3 Pa.s ) close to:
EASY
A glass capillary tube is of the shape of a truncated cone with an apex angle α so that its two ends have cross-sections of different radii. When dipped in water vertically, the water rises in it to a height h, where the radius of its cross-section is b. If the surface tension of water is S, its density is ρ, and its contact angle with glass is θ, then the value of h will be (g is the acceleration due to gravity)

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MEDIUM
A hollow spherical shell at outer radius R floats just submerged under the water surface. The inner radius of the shell is r . If the specific gravity of the shell material is 278 with respect to water, the value of r is:
HARD
Air (density ρ ) is being blown on a soap film (surface tension T ) by a pipe of radius R with its opening right next to the film. The film is deformed and a bubble detaches from the film when the shape of the deformed surface is a hemisphere. Given that the dynamic pressure on the film due to the air blown at speed v is 12ρv2, the speed at which the bubble formed is
HARD
Water from a pipe is coming at a rate of 100 liters per minute. If the radius of the pipe is 5 cm, the Reynolds number for the flow is of the order of: (density of water = 100 kg/m3, coefficient of viscosity of water =1 mPa s)
HARD
Consider the wall of a dam to be straight with height H and length L. It holds a lake of water of height hh<H on one side. Let the density of water be ρw Denote the torque about the axis along the bottom length of the wall by τ1. Denote also a similar torque due to the water up to height h2 and wall length L2 by τ2. Then, τ1τ2 (ignore atmospheric pressure) is
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Consider the configuration of a stationary water tank of cross-section area A0 and a small bucket as shown in figure below;

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What should be the speed v of the bucket, so that the water leaking out of a hole of cross-section area A (as shown) from the water tank does not fall outside the bucket?

(Take, h=5 m, H=5 m, g=10 m s-2, A=5 cm2 and A0=500 cm2).

EASY

A cylinder of radius a and height H is filled with a liquid to an unknown height h. When it is rotated at an unknown constant angular velocity ω, the base of the cylinder gets exposed when the liquid just starts spilling out, as shown in figure.
(a) Find the height h of the liquid.
(b) Find the angular speed ω of the cylinder.
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MEDIUM
Two capillaries of length L and 2L and of radii R and 2R respectively are connected in series. The net rate of flow of fluid through them will be (Given, rate of the flow through single capillary, X=πpR4/8ɳL )
EASY

Consider the following statements:

1. Taking into account, the fact that any object which floats must have an average density less than that of water during World War 1, a number of cargo vessels were made of concrete.

2. Concrete cargo vessels were filled with air.

3. A ship floats higher in the water on a high-pressure day than on a low-pressure day.

4. Floating of the ship in the water is not possible because of the buoyancy force which is present due to pressure difference.

Which of the statements given above are correct?

EASY
The terminal velocity vr of a small steel ball of radius r falling under gravity through a column of a viscous liquid of coefficient of viscosity η depends on the mass of the ball m, acceleration due to gravity g, coefficient of viscosity η and radius r. Which of the following relations is dimensionally correct?
MEDIUM
A jet of water having velocity=10 m s-1 and stream cross-section=2 cm2 hits a flat plate perpendicularly, with the water splashing out parallel to plate. Find the force that the plate experiences